Indeed, you can use Git. The source code can be “Filed Out” to Git and “Filed In” from Git.
The thing with the image is that each developer in the team works on their own piece of the application. At some point, every developer’s work must be integrated back into the main trunk of the project. This is no different from how most software projects in other languages work.
In fact, you can think of the image as a system wrapper around an IDE. The IDE is much like any other IDE (Visual Studio, Eclipse, etc.), except that it’s much, much simpler and it supports live coding.